Automatic well-drilling mechanism



March 11, 1952 Filed June 30, 1945 C. M. OLEARY AUTOMATIC WELL DRILLING MECHANISM 3 Sheets-Sheet l INENTOR.

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March l1, 1952 c. M. O'LEARY 2,589,118

AUTOMATIC WELL DRILLING MECHANISM Filed June 30,- 1945 5 Sheets-Sheet 2 iiD 0600 7M 60o E/rrre 5f/ggd KFM. M E E INVENTOR. /22 @d/*Zes )57: ear-gf, BY

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March 11, 1952 C, M Q'LEARY AUTOMATIC WELL DRILLING MECHANISM 3 Sheets-Sheet 3 Filed June 50, 1945 Fill. .illll [N VEN TOR. Ca/*Zep* /earcg.

75W BY ,5% y/f Patented Mar. 11, 1952 AUNITED STATES PATENT OFFICE AUTOMATIC WELL-DRILLING MECHANISM Charles M. OLeary, Detroit, Mich.

Application June 30, 1945, Serial No. 602,620

(Cl. Z55- 19) 15 Claims. l

The present invention relates to an apparatus for automatically controlling the pressure of the drilling bit during oil well drilling operations in accordance with fluctuations in the driving torque required for the rotary table of a conventional rotary drilling machine in order to maintain optimum drilling conditions and avoid the building up of an excessive torque on the rotary table.

It is conventional practice to control the drill bit pressure by means of a hand brake associated with the hoisting drum that is connected by a drllling line through suitable sheaves to the drill stem. The brake is manipulated in such a manner that the hoist supports substantially all the weight of the drill stem, leaving only a minor portion acting on the bit to provide the desired degree of bit pressure. In view of the serious diiliculty of maintaining the drill bit pressure constant by such means, as well as the difiiculty of relieving the bit pressure when the torque on the rotary table increases, many attempts have been made to devise apparatus for automatically supporting the proper proportion of the drill stem weight, to the end that the bit pressure will remain on the desired general level and will fluctuate only in accordance with fluctuations in table torque induced by the resistance offered to rotation of the drill stem. Many of the forms of apparatus heretofore proposed are exceedingly complicated and expensive, but in general, they employ two basic principles of operation. The rst class of mechanisms for this purpose incorporates a diiierential drive from the engine to the table and the hoisting drum, with the result that the drum torque automatically uctuates in direct proportion to the table torque. In the second class an attempt is made to control'the drill bit pressure by varying the speed ofthe hoisting drum in accordance with fluctuations in the table' torque.

The rst class of prior mechanisms is totally unsatisfactory for the reason that the allowable percentage fluctuations in table torque greatly exceed the percentage fluctuations allowable on the drum torque. Thus, in deep well drilling the drill bit pressure may be only two or three percent of the total weight of the drill stern and, consequently, an increase of two or three percent in the table torque would reduce the drill bit pressure to zero. Much ygreater percentage :fluctuations in the table torque occur during normal operation. Accordingly, all such mechanisms, either apply too much drill bit pressure or are constantly lifting the drill bit @if the formation and thus interrupting the drilling operation. l

'Ihe principle upon which the second class of prior mechanisms operates is erroneous in that the drill bit pressure is not proportional to the speed of penetration of the bit or the speed of rotation of the hoistingrdrum. lActually, for a given drill bit pressure, the rate of penetration of the bit varies widely, depending upon the character of the formation through which it is passing, as well as other characteristics, such as the sharpness of the bit, and the circulating mud pressure. Consequently, all mechanisms which seek to control drill bit pressure by varying the speed of the drum in accordance with fluctuations in table torque have proved unsatisfactory.

i Moreover, many of the prior mechanisms of this class employ pressure or force responsive control devices for automatically adjusting the druml speed. All such mechanisms are subject to objectionable hunting characteristics.

Accordingly it is the object of the present invention to provide apparatus which is automatically effective to maintain the drill bit pressure at the desired general level, subject only to fluctuations in accordance with allowable variations in the rotary table torque and which operates independently of the rate of penetration of the drill bit and the rate of movement of the hoisting drum.

Another object of the invention is to provide a mechanism of the above type which does not embody force or pressure responsive control devices and which, therefore, is not subject to hunting.

Another object of the present invention is to provide several practical forms of apparatus of the above type, all of the elements of which may comprise standard commercial items of equipment which are simple in construction, rugged and foolproof in operation.

Another object of the present invention is to provide apparatus of the above type which is exceedingly flexible in operation and which may be readily adjusted to meet any desired conditions of use, including a progressive increase in the drum torque as the drilling operations progress deeper without altering the desired balance between table torque and drill bit pressure.

Another object of the present invention is to provide a specific mechanism of the type mentioned which may be readily adapted to either automatic drilling or drilling in accordance with conventional practices, as desired by the operator.

Other' objects and advantages of the invention will become apparent from the following speoipended claims.

In the drawings,

Figure l is a diagrammatic illustration of one form of the invention;

Figure 2 is a similar diagrammatic illustration of another form of the invention;

Figure 3 is a similar diagrammatic illustration of still another modification of the inyention;

Figure 4 is a somewhat more detailed diagrammatic illustration of acomplete automatic drilling unit incorporating means to permit operation of the drilling machine by several conventional methods;

Figure 5 is a sectional view showing one form of differential mechanism which may be employed in the mechanism of Figures 1, 2, 3, and 4;

Figure 6 is a longitudinal sectionA through aV the overdrive and clutch mechanism employed'- in the apparatus of Figure 4;

L Figure 9' is a graph of torque and speed characteristics for atypical engine and torque converter which might be employed in the mechanisms ofthe present invention;

FigureV l0v is a diagrammatic view, partly in section, showing one type of engine speed control mechanism which may be employed in certain' embodiments ofi the present invention.

In accordance with thepreferred forms of the present invention, the hoisting drum is supplied withadrill stem supporting torque which is transmitted froml an engine or other suitable source of' motor powerV through a drive connection which will transmit a fixed amount of torque at' a'ny-E given engine. speed so long as the drum speedf is'negligible; and the table is driven either from the same engine or a separate source of power through a differential mechanism which is so arranged that an additional torque which is' substantially proportional to the table torque.

is alsoftransmitted through the differential to the hoisting drum in a direction to help balance the weight of the drill stem. As will'. become apparent from the following more detailed. description, when a single engine is used' the. engine speed' is either-maintained constant so that the torquei transmitted through the fixed torque driveimechanism remains constant, or the torque multiplication in the drive connection between thedifferential' mechanism and the hoisting drumlis so selected as to compensate for the reduction in. drum torque which would otherwise occur as the result of a reduction in engine speed caused by an increase in table torque.. Ineither case, by selection of the proper torque multipli'- cation.ratiosV in the respective drive connections the apparatusmay be so. constructed as; to produce a xed increase. in drum torque incident to any given increase, in table torque. over. a wide range in total? drum torque. As a result the rotating torque on thel drill stem and the drill bit pressure. will tend.' to balance automatically and maintain; ai substantially constant table torque ofl anyl desired value.

The` preferred form. of.- torque transmitting mechanism between the engine and the drum is` ahydrokinetic torque converter due to 'its advantageous: torque multiplication., I-Iydrokinetic torque. transmittingv devices fall in two classes. The first class is the couplers, whichn consist in.

an impeller corresponding to a centrifugal pump and a driven element corresponding to a hydraulic turbine. This class transmits torque, but the torque transmitted to the driven element never exceeds that delivered to the impeller. The second class is the torque converters, which are basically similar to the couplers except that they include as an additional element at least one set of stationary reaction vanes. The converters may have one or more stages of turbine vanes on the driven element with a set of stationary reaction vanes in advance of each turbine stage or each stage except the first. As the result of the stationary reaction vanes, the torque converter has the inherent capacity of multiplying torque and acts as an automatic innitely variable transmission which provides a torque multiplication generally proportional to the speed of the impeller for any given speed of the turbine or driven element. While this torque multiplication is off great' advantage in that it eliminates the necessity' of considerableY torque multiplication 1n other portions of the drive mechanism,V

a hydrokinetic torque coupler: or any form; of

1 electric or mechanical coupler which will transmit a torque that varies with the engine speed when the. output of. the coupler is substantially stationary may be employed. The torque converter, or other form of coupling, however, is not operated in the usual manner as a driving connection, but more nearly operates as a brake, because its output shaft will rotate reversely to the input shaft as the drill bit penetrates deeper. During rotary drilling operations the drum speed, due to drill bit penetration, vis always so slow, compared with the input speed of the converter, that its effect on the transmitted torque is negligible. Moreover, no means are employed to correct for these slight variations in drill bit presf sure and therefore the apparatus is free from The simplest form of the apparatus is illustrated diagrammatically in Figure 1. As there shown, the engine I is connected by a sprocket and chain drive 2 to the input shaft 3 of a differential mechanism 4. One output shaft 5 of the differential 4 is connected by a sprocket and chainY drive 6 to the drivey shaft 'i' of a conventional rotary table adapted to rotate the drill stem during drilling operations. The other output shaft 9, which is illustrated as a sleeve surrounding shaft 3, is connected by a sprocket and chain drive l0 to the shaft l of a hoisting drum l2 adapted to support or hoist the drill stem. The engine i is also connected to the drum shaft il by a hydrokinetic torque converter I3 and a sprocket and chain drive lll.L The engine may bc any suitable. source of power having control means tov vary the torquedevelopedat any given speed and having for any given control setting a torquecurve which falls. as the speed increases. An internal combustion engine which develops its maximum torque at a speed well below the maximum operating speed is preferred. However, an electric motor having a power controller may be used.

The mode of operation of the apparatus and the principles governing the design of apparatus to meet any desired conditions may bestv be set forth by reference to the torque speed curves illustrated in Figure 9. Curve a represents the torque-speed curve of an internal combustion engine at wide open throttle, while curve b is the torque-speed curve of the same engine with a partially closed throttle; Curve o is the input torque-input speed curveof a hydrokinetic torque converter when the output shaft of the converter is substantially stationary. Curve c is dependent solely upon the characteristics of the torque converter and is, therefore, the same for any given torque converter, whether the engine is running at wide open or closed throttle. The particular curves illustrated are only generally representative, and it will be understood that in practice the actual curves of the engine and converter which are to be incorporated in' the apparatus should be used as the basis for the design. These will vary widely, depending on the sizes and designs of the engine and converter.

Since most converters operate more effectively at higher input speeds than that of the engine whose curves are illustrated in Fig. 9, an overdrive may be provided between the engine and converter when a slow speed engine is used. In

. that case, the curve c will represent the actual converter input torque multiplied by the overdrive speed ratio and thus will represent a higher torque than the actual converter input torque. 'I'he converter output torque for all negligible output speeds will be a fixed multiple of the input torque.

From the curves of Fig. 9, it will be seen that for any given engine speed, the portion of the total engine torque represented by line c will be absorbed by the converter and the remainder will be transmitted to the differential 4. When the engine is operating at full power, represented by line a, the torque transmitted to the differential is measured by the distance between lines a and c. This value is separately plotted at e. Line d represents the corresponding values of torque delivered by the engine to the differential 4 when the engine is throttled down to line b.

From these curves it will be apparent that if the engine is operating at 1000 R. P. M. with a xed wide open throttle, the torque delivered to the drum through the converter is a maximum of about 1310 foot-pounds and the torque delivered to the differential is a minimum of about 160 foot-pounds. If the table encounters an increased resistance, the table torque will build up. However, this can only be done by slowing up the engine and thereby decreasing the torque transmitted to the drum through the converter. Thus, the drum will receive less torque from the converter and more torque from the differential. If the torque multiplication factors in the two parallel drives to the drum are properly selected, the total drum torque can be made to increase on any given increase in table torque by an in that portion of the drum torque transmitted,

through the torque converter.

One method of determining the proper torque multiplication ratios for the apparatus may best be demonstrated by an illustrative example. Accordingly, it will be assumed that the desired operating conditions call for a table torque of 600 lbs. when the drill bit pressure is '10,000 lbs., and a reduction in the drill bit pressure to zero when the table torque reaches 1400 lbs. It will also be assumed that the maximum Adesired table speed is 278 R. P. M. and thatv the maximum drum torque is to be 50,000 lbs. (which corresponds approximately to the torque imposed by the drill stem at a depth of 15,000 feet when six lines are used on the sheaves). It will also be assumed that the maximum engine speed is 1000 R. P. M.

6 and that the engine and torque converter have the characteristics indicated in Fig. 9.

From the above assumed maximum table speed and the maximum engine speed, it is apparent that the total torque multiplication between the engine and the table must be To produce a table torque of 600 lbs. with a 3.6 torque multiplication requires that the engine Supply 600 -l lbs. torque The particular engine and converter whose characteristics are indicated in Figure 9 were selected because they satisfy that condition.

When the table torque reaches 1400 lbs., the engine must deliver to the dilerential l From curve c it is apparent that this cannot be achieved until the engine speed drops to 925 R. P. M. 4At that speed the torque delivered by the engine to the converter will be 1000' lbs. Now in order to decrease the bit pressure 10,000 lbs. when six lines are employed on the hoist sheaves and the drum diameter is two feet, it is necessary to increase the drum torque by lbs. torque Therefore, if Rc equals the total torque multiplication for the engine torque which is transmitted to the drum through the converter and Rd equals the total torque multiplication for the torque which is transmitted from the engine to the drum through the differential, then the following two equations can be obtained:

(l) 1150RC|166 Rd=50,000 (2) 1000Rc-l-390 Rd=51,666

Rczfisoltd substituting:

@(51,666 390RD) -I- 166RD=50,000

Equation 1 represents an equality betweenA the summation of the two separate torques upon the drum and the total torque on the drum when the drill bit pressure is ten thousand (10,000) lbs., the engine speed is one-thousand R. P. M. and the engine throttle is wide open. In Equation 1 the engine torque to the converter is 1150 lbs.,

as shown on curve c of Figure 9, and the engine torque to the differential is 166 ft.lbs.

Equation 2 represents an equality similar to Equation 1 with an engine speed of 925 R. P. M. and wide open throttle.

As indicated above, from the two equations given it is apparent that Rc, or the total torque multiplication for the engine torque which is transmitted to the drum through the converter, should be 38.7 while Rd, the total torque multi` plication for the torque which is transmitted from the vengine yto the drum `through the differential, should vbe 33.

Suitable torque multiplication can be provided in the two drives in any desired manner to produce the above overall ratios. It should be noted, however, that in the case of the differential drive to the drum, the added torque multiplication should be so inserted that it leaves the torque ratio between the engine and the table at 3.6-1. Part of the differential torque multiplication between the engine and the drum may be incorporated in the differential itself and the balance in the sprocket and chain drive l0. In the case of the converter-drum drive, part of the multiplication is achieved by the torque converter, less any torque reduction in the overdrive, if any, and the balance in the sprocket and chain drive I4.

An important feature of the present invention resides in the fact that for given ratios of torque multiplication in the drive connections, the amount of weight which can be balanced by the hoisting drum may be varied widely by simply adjusting the engine throttle position without changing the range of variation in drill bit pressure for a given variation in table torque. Thus, with the above ratios, if the engine throttle is closed to the condition indicated by curve b in Fig. 9, the engine will drop to a speed of 790 when the table torque is 600 lbs. and to a speed of '710 when the table torque is 1400' lbs. At '790 R. P. M., the drum torque (from curves c and e) is:

At 710 R. P. M., the drum torque is:

The increase in drum torque for the same range in table torque is, therefore, 1779 lbs., crapproximately the same as at wide open throttle in spite of the fact that the drum torque is more than 30% less. Thus, by simply shifting the throttle position, the apparatus will automatically take care of drilling operations from a depth of about 11,000 feet to about 15,000 feet.

The magnitude of this range of adjustment depends on the range in engine speed available above the engine speed of maximum engine torque. Consequently, this form of the invention requires an engine which achieves its maximum torque at a speed substantially lower than its maximum operating speed. Any desired overall increase in drum torque is achieved by opening the throttle of the engine, and the desired drum torque is automatically maintained by simply xing the engine throttle in the desired position. f

In order to obtain a further change. in drum torque for a given table torque, it is necessary to change the ratio of torque multiplication between the hydrokinetic torque transmitting device and the drum. Thus a decrease in that ratio decreases the drum torque for a given enginel speed and vice versa. This change in speed ratio may be eiected in any desired manner in the connection between the hydrokinetic torque transmitting device and the drum, as by a changespeed transmission or simplyy by changing drive sprockets in the chain and sprocket drive I4. However, with this form of the invention, any decrease in the torque ratio between the hydrokinetic torque transmitting device and the drum will increase the amount of variation in the drum torque for a given change in table torque, and

vice versa. Therefore, if it is desired to maintain the amount of variation in drum torque at a constant value, it is necessary to reduce the torque multiplication of the table reaction torque which is transmitted to the drum from the differential when the torque ratio between the hydrokinetic torque transmitting device and the drum is reduced, and vice versa. This is necessary because otherwise on a decrease in drum torque ratio the table reaction torque on the drum will over-compensate for the decrease in converterdrum torque 'due to a reduction in engine speed.

For example, if the torque ratio between the engine and the drum through the converter is reduced to 3.87 and the range in table torque and drill bit pressure is to be the same, the above method of calculation indicates that the torque multiplication between the engine and the drum through the differential should be 10 to 1. At wide-open throttle the total torque on the drum will be 6120 lbs. when the engine is operating at 1000 R. P. M. and the table torque is 600' lbs. and will be 7786' lbs. when the engine is operating at 925 R. P. M. and the table torque is 1400 lbs. The difference in these two drum torques is 1666' lbs. When the engine is throttled-down to the condi-tion indicated by line b on Fig. 9, the total drum torque will vary from 4535' lbs. to 6235 lbs. for the same table torque range, a difference of 1700 lbs. It is obvious that for intermediate torque multiplication ratios intermediate drum torques can be achieved. A total of about eight properly selected torque ratios for the converter drum torque will cover the entire range of drilling from 1000 feet to 15,000 feet in depth with the same drill bit pressure and table torque range. Fewer adjustments are required if the hole is started with a larger bit which will require greater pressure. Unless very close control is required on the drill bit pressure, only half as many torque ratio changes are required for the engine drive through the differential to the drum.

If it is desired to increase the torque on the table at the expense of table speed, or vice versa,

that may be accomplished by ,simply changing the torque ratio between the differential and the table without aiecting the mode of operation of the apparatus. If the table torque ratio is decreased, the apparatus may be operated over the original table torque range by decreasing the engine speed and vice versa. For all table torque ratios, a given percentage change in table torque will produce approximately the same change in drill bit pressure so long as the remaining torque ratios are unchanged. Therefore, any given design of apparatus is quite flexible and may be adjusted or modified to meet varying conditions without diiiculty.

The change in torque ratio between the engine and drum through the converter which is necessary to increase the range in drum torque, beyond that which can be achieved by engine throttle adjustments, may be achieved by simply changing the speed ratios in the change speed transmission conventionally provided on oil well hoisting drums. Thus, as pointed out hereinafter in connection with other embodiments of the invention, a change speed transmission may be located at any place in the drive between the converter and the drum. The necessary changes in speed ratio between the engine and the drum through the differential can be taken care of by a second change-speed transmission located any where between the differential and the drum. but

. by adjusting the throttle position with the rst form of the invention. 'I'his second form of the invention has the further advantage that the form of the engine torque curve plays no part in the operation of the apparatus and hence the engine may be chosen for other characteristics. For example, it is advantageous during the operation of pulling the drill stem through a torque converter drive to employ an engine whose maximum torque is reached fairly near maximum speed, and with the second form of apparatus such an engine may be used.

Any desired form of adjustable speed governor can be used on the engine l to produce an apparatus of the second type. One such governor mechanism is illustrated more or less diagrammatically in Fig. 10. As there indicated the engine is provided with a governor mechanism indicated generally at l having a shaft l connected to the engine and driven thereby at a speed directly proportional to engine speed in the usual manner. rThe shaft I6 is supported in any suitable bearings, such as the bearing l1, and is held against downward axial movement by a ball thrust bearing I8, located between the bearing l1 and a collar i9 formed on the shaft I6. The governor is of the conventional yball type having an axially slida'ble sleeve 20 connected by a plurality of pivoted arms 2! which in turn are pivotally connected to the iiyball weights 22. A spring 23 normally tends to separate the sleeve 23 from the collar I9 and thus to draw the weights inwardly. The tendency to fly outwardly under the infiuence of centrifugal force compresses the spring 23 and moves the sleeve downwardly. A second sleeve 24 is slidably mounted upon the shaft I6 and is connected to a yokelike lever 25 by a pin and slot connection 26, indicated in dotted lines. The lever 25 is pivoted on any suitable stationary pivot 32. Its opposite end is connected by means of a link 21 to a lever 28 on the shaft 29 of a butterfly valve located in the intake manifold 3l of the engine in the usual manner. As will be understood, the Valve 3G is the throttle valve of the engine. A third sleeve 32 is also slidably mounted on the shaft l and connected by a pin and slot connection to one arm of a bell crank lever 33 the opposite arm of which is connected by means of a link 35i to a control lever 35 having a latching mechanism indicated generally at 33 for securing it in any desired adjusted position. A spring 3l is positioned between the sleeves 24 and 32, and a thrust bearing 38 is positioned between the sleeve 24 and the sleeve 20.

The spring 31 normally acts to force the sleeves 2G and 2li downwardly and thus to assist the centrifugal weights 22 in closing the throttle valve 36. 'Ihe spring 23, which is stronger than the spring 3?, normally acts to resist outward movement of the weights 22 and tends to open the throttle valve. Adjustments of the position of sleeve 32 eiected by means of the lever 35 vary the position at which the sleeves 20 and 24 will stabilize at any given speed of rotation of the shaft I6, and, consequently, vary the throttle opening for any given speed of shaft I6. As a result, the mechanism will maintain the engine at a substantially constant speed, which speed may be adjusted by adjusting the position of the control lever 35. For any given adjustment of the lever 35, the throttle valve 35 will open or close, depending upon the torque imposed upon the engine, without any substantial change in the engine speed.

With this second form of apparatus it will be apparent that the torque transmitted from the engine through the torque converter to the drum will always remain substantially constant for any given adjustment of the lever 35, due to the fact that the engine speed remains substantially constant. When the table encounters increased resistance the engine will not slow down a substantial amount, as in the iirst form of the invention. but will slow down only a negligible amount which will cause the throttle to open, thus increasing the torque delivered by the engine. Since none of the increased torque can be delivered to the converter at that speed, all of the increase is transmitted to the differential and, consequently, there is added to the drum torque through the sprocket and chain connection lil, an additional torque directly proportional to the table torque. If the torque multiplication from the engine through the differential to the hoisting drum is so selected as to impose the desired increase in drum torque for a given increase in table torque, that balance will remain constant at all engine speeds and will -be unaffected by changes in the torque ratio between the engine and the hoisting drum through the torque converter. This greatly facilitates adjustments to accommodate drilling at different depths.

It will be appreciated that in Iboth forms of the invention described above, the converter output shaft will be rotated reversely at a very low speed during all normal drilling operations and that therefore all of the power delivered to the converter is turned into heat. Accordingly, the cooling mechanism for the operating liquid of the converter must be adequate to dissipate all of the heat generated during sustained drilling operations. The preferred form of cooling mechanism for this purpose is a differential cooling mechanism constructed in accordance with applicants copending application Serial #571,656, led .Ianuary 6, 1945, and now abandoned or the similar mechanism shown in applicants copending application Serial No. 602,619 filed concurrently herewith.

A third form of the invention is illustrated dia,- grammatically in Fig. 2. As there shown, the general arrangement is identical to that of Fig. 1, except that a torque converter 39 is inserted in the table drive connections between the engine and the differential. The use of a torque converter in this drive connection is advantageous because it provides a yielding drive connection which will absorb shock loads on the system. It is of further advantage when employed with an apparatus of the rst type mentioned, wherein the system is balanced by a xed throttle posiltion, as distinguished from a speed governor, due to the fact that it further reduces the number of changes in torque multiplication which are required in the drive .between the engine and the drum through the differential. This follows from the fact that when the output shaft cfa converter is loaded up, the output torque of the converter increases at a greater rate than the input torque. Consequently, for a given change in table torque there will be a smaller increase in the torque imposed upon the engine and consequently less reduction in the speed of the engine than in the case when a direct mechanical connection is provided between the table and the engine.

In all other respects the third form of the invention is similar in construction and operation to those previously described and may employ either a governing engine like that described in connection with the second form of invention or an engine which is simply controlled by an adjustable throttle or fuel consumption control device.

An alternative arrangement which avoids the necessity of changing the torque multiplication ratios between the differential mechanism and the drum is illustrated diagrammatically in Fig. 3. As there shown, the arrangement is similar to the previously described forms of the invention, except that two engines are employed. 'I'he engine 40 corresponds to the engine I of Fig. 1 in that it operates through the torque converter to apply a drill stem balancing torque to the hoisting drum, which is proportional to the engine speed. The engine 49 may be controlled by an ordinary throttle control, because, in conjunction with the torque converter 4l, the engine will operate at a constant speed for any given setting of the throttle. An auxiliary engine 42 is connected to the input shaft 43 of the differential mechanism 44, and the differential is connected in the manner previously described to the rotary table and to the hoisting drum. It will be apparent that when this arrangement of apparatus is employed, variations in the torque applied to the rotary table by the engine 42 will not affect the speed of engine 40 and consequently will not alter the torque supplied to the drum by the engine 4I] and the torque converter 4I. Consequently, the magnitude of the variations in drill bit pressure for a given variation in table torque will remain the same for all speed adjustments of the engine 40 and, therefore, for a wide range of drum torques. The provision of a separate source of power to drive the table facilitates adjustments of the table speed and torque. In all other respects the fourth form of the invention illustrated in Fig. 3 is similar to those previously described. It will be understood that, if desired, a torque converter may be provided between the engine 42 and the rotary table.

In actual practice in each of four forms of the invention described above suitable control clutches will be provided to permit operation of the apparatus in accordance with the usual practice. Moreover it is necessary to provide a selectively operable reverse gear mechanism in the table drive in order to provide for reverse rotation of the table. It is desirable to employ the engine I or the corresponding engines in the other forms of invention, as at least part of the source of power required to hoist the drill stem during drill stern hoisting operations. It is preferred, however, to employ a plurality of engines for that purpose and, consequently, means will be provided to connect the engine I, along with such additional engines as are necessary, to the drum during hoisting. At that time the connection between the engine and the rotary table or between the differential mechanism and the drum must be broken.

In Fig. 4 is illustrated diagrammatically and in somewhat greater detail a complete arrangement of mechanism embodying the lprinciples of the forms of invention shown in Fig. 1 and incorporating the necessary change-speed and reverse transmissions as well as the necessary control clutches required to carry out all normal drilling operations, either with or without the automatic control of the drill bit pressure in response to variations of the table torque.

Thus, referring to Fig. 4, there is provided a hoisting drum 45 which may be of ordinary construction and is connected by means of the usual cable and sheaves to the drill stem to support or hoist the same. The drum is provided with the usual manually controlled brake bands 46. An engine 41 having an output shaft 48 is connected to the hoisting drum through an over-drive and clutch mechanism 49, hereinafter described in greater detail, a hydrokinetic torque converter 50, a sprocket 5l, chain 52, a double sprocket 53, chain 54, a sprocket 55, a pneumatically operated clutch indicated diagrammatically at 56, changespeed transmission 51, and a sprocket and chain connection 53. The double sprocket 53 is normally freely rotatable upon a shaft 59 but may be clutched to the shaft 59 by means of a pneumatically operated clutch 60 when desired.

The engine 41 is also connected by sprocket and chain connection 6I and a pneumatically operated clutch 62 to the input shaft 63 of a differential mechanism 64. 'I'he shaft 59 is one of the output shafts of the differential B4 and is connected through a change-speed and reverse transmission and a sprocket and chain connection 61S to the rotary table 61. The other output shaft 68 of the differential 64 is connected by means of a sprocket and chain connection 69 and a pneum'atically operated clutch 10 to the output shaft 1| of the transmission 51 and, consequently, transmits a torque proportional to the table torque to the hoisting drum 45 through" the sprocket and chain connection 58.

The preferred form of differential mechanism 64, which also may be used in the previously described formation of the invention is illustrated in Fig. 5. As there shown, the differential comprises a casing 12 in which is journaled the previously mentioned differential input shaft 63. Shaft 63 carries a gear 33 which forms the central or sun gear of a planetary gear set including an internal ring gear 13 and a plurality of planet gears 14. The planet gears 14, only one of which appears in the drawing, are journaled in suitable bearings on a carriage 15 fixed to the output shaft 59 and mesh with the gears |33 and 13. As a result of this arrangement rotation of the input shaft 62 in the direction indicated by the arrow in Fig. 5 will tend to rotate the output shaft 59 in the same direction at a lower speed when the gear 13 is held relatively stationary, but the force applied to the gear 13 tends to rotate it in the opposite direction, and that force is proportional to the torque transmitted from the shaft 63 to the shaft 59. Any suitable means may be provided for transmitting the torque applied to the gear 13 to the hoisting drum 45 in a direction to support a portion of the weight of the drill stem connected to the drum.

In order to reverse the direction of the torque applied to the gear 13 and also to multiply that torque in order to increase its drill stem supporting effect, a planetary reverse gear set is included within the differential 64 illustrated in Fig. 5. Thus, as shown in that gure the gear 13 is carried by a sleeve 16 which is journaled on a sta tionary web 11 carried by the casing 12. Sleeve 16 is provided with an external spur gear 18 which meshes with a plurality of spur gears 19 journaled on the web 11. The gears 19 in turn are in mesh with an internal gear 80 which is Xed to the output shaft 68 of the differential. The shaft 68 carries a sprocket 8| adapted to carry the aforementioned chain 69. It will be noted that the input shaft 53 is journaled in suitable bearings carried by the output shaft 59, the sleeve 16, and the output shaft 88. As a result of these connections the table reaction torque applied to the gear 13 is reversed and multiplied before it is applied to the output shaft 1| of the transmission 51 and from there to the hoisting drum.

It will be understood that the present invention is not limited to the use of a differential mechanism of the particular type illustrated and described herein but that any form of driving connection from the engine to both the drum and the rotary table may be employed so long as it transmits to the drum a torque proportional to the table torque and in a direction to assist in supporting the weight of the drill stem. For this purpose a hydraulic differential drive may be employed, if desired.

The change-speed and reverse transmission 85 Which is connected to the output shaft 59 of the differential may be of any suitable construction effective to change the torque multiplication ratio between the shaft 59 and the table and to provide a reverse drive in that connection. However, the preferred form of transmission 95 is illustrated in Fig. 6. As there shown, the transmission comprises a casing 82 having a bearing 83 at one end for supporting input shaft 59, an intermediate web 8d having a bearing 85 for supporting an intermediate shaft 88 and bearing 81 for supporting an output shaft 88. Extremities of the shaft 86 are supported in a bearing 89- carried by the shaft 88, and a bearing 90 by the shaft 88 and the extremity of input shaft 59. The inner end of shaft 59 carries a spur gear 9| which is connected to a larger spur gear 92 by means of a plurality of clusters of planet gears, each of which includes a spur gear 93 and a smaller spur gear 94 xed together and journaled on a cage 95.

The planet cage 95 is journaled by means of suitable bearings on the shafts 86 and 5S, and

the cylindrical periphery of the cage 95 co-operi ates with a plurality of one-way clutch blocks 98 which are mounted in suitable pockets formed in casing 82 in the manner set forth in greater detail in applicants copending application, Serial It is speed during which operation the planet cage will be held against rotation by the one-way clutch blocks 95. When it is desired to provide a direct drive Ibetween the shafts 59 and 86, planet cages are held against rotation about their own axes by means of a clutch mechanism which includes a plurality of cone clutch elements 91, one for each planet gear cluster, and a corresponding number of cone clutch elements 98 carried by ,lutch ring 99 which is slidable .and rotatable upon the shaft 59. The clutch ring 99 is normally held in its right-hand or clutch release position by means of a spring |00, but may be shifted into engaged position by means of a sliding annular cylinder |0| which acts upon the clutch ring through a thrust bearing |02. The sliding cylinder |0| receives a stationary annular piston |08 which is provided with a passageway |04, communicating with the interior of the cylinder ||l| and a conduit |95 for the supply of fluid under pressure to actuate the cylinder. When pressure fluid is applied through the conduit |05 by any suitable control means, the clutch plate 99 will be shifted to the left, thereby causing engagement between the clutch elements 91 and 98 which will prevent rotation of the planet gear clusters about their own axes and thus provide a direct drive connection between the shafts 59- and 85. It will be apparent that any desired number of two-speed planetary transmission units of the type so far described may be employed in the transmission 65, depending upon the number of speed changes required. However, for most ordinary operations one such planetary transmission is sufficient.

The intermediate shaft 88 is connected to the output shaft 88 by means of a selectively operable planetary reverse gear unit comprising an external spur gear |06 on the shaft 86, an internal gear |01 fixed to the shaft 88, and a plurality of planet gears |08 which are journaled in suitable bearings in a planet cage |09 journaled on the shaft 86 by means of bearings l0. The planet cage |09 is provided with a brake flange adapted to co-operate with a fluid operated brake band ||2. As best shown in Fig. 7, one end of the brake band ||2 is anchored by means of an adjustable fixture, indicated generally at ||3, and the other end is connected to a piston ||4 mounted within a cylinder ||5. A brake release spring ||6 is positioned within the cylinder ||4 and normally acts to shift the piston in a brake releasing direction. A conduit ||1 for fluid under pressure communicates with the opposite end of the cylinder, with the result that on an application of uid under pressure to the conduit ||1 the brake band I2 will be applied to hold the planet cage |09 against rotation. Under these circumstances, the output shaft 88 will be rotated reversely with respect to the shaft 86 but at a lower speed.

In order to establish a direct forward drive through the planetary reverse gearing, the brake band ||2 is released and the planet gears |08 held against rotation about their own axes by a fluid operated clutch mechanism, indicated generally at ||8 and similar in construction and operation to that previously described in connection with the planet clusters 93 and 94. It will be obvious that any suitable form of fourway control valve may be employed for alternately applying pressure fluid to the conduits ||1 and ||9.

Any suitable clutch may be provided between l the engine 41 and the torque converter 50 but if the engine is a relatively slow speed engine, it is desirable to provide an overdrive in the connection between the engine and the torque converter in order to increase the efficiency of the latter. Consequently, such an overdrive connection, which also performs the functions of a clutch, is illustrated diagrammatically at 49 in Fig. 4, and one suitable form of construction is illustrated in greater detail in F'ig.` 8.

. form or According to Fig. 18, it will be observed rthat the .combined overdrive and clutch, which is mounted in a suitable casing |26, shown fragmentarily in Fig. 8, comprises an input shaft 48 from the engine and an output shaft |2| which leads to the torque converter. These two shafts, are provided with gears |22 and |23 which are connected by means of a plurality of planet gear clusters, each incorporating a pair `.of gears |24 and |25, fixed together and journaled in a cage |26 which is journaled for rotation about the shafts 48 and |2I. The relative size of the gears |22 through |25 is such that a Vgiven rotation of the input shaft 48 produces a more rapid .rotation of the output shaft |2| in .the same direction when the planet cage |26 tis held stationary. Means comprising a, brake band |21 are provided to selectively hold the planet cage |26 against rotation and thus provide ja drive connection between shafts 48 and .|2|. The brake .band |21 may be constructed and operated by fluid pressure in the manner indicated more fully in connection with brake band |I.2 of Fig. 1, the operating cylinder for the brake band being indicated diagrammatically at V|28 in Fig. 4. It will be obvious "that upon release from the brake band |21 the cage |26 will be free to rotate and, consequently, no drive torque can be transmitted from shaft 43 to .shaft |2|. 'The mechanism, therefore, operates in that .case as a clutch for disconnecting the engine from the torque converter.

It will be understood that for hoisting operations a plurality of engines, in addition to the engine 41, will be employed to rotate the drum. Consequently, means in the form of a sprocket and chain connection |29 is indicated fragmentarily in Fig. 4 for connecting the additional engines to the output shaft of the torque converter 50. The sprocket on the output shaft |30 of the torque converter, which carries the chain |29, is normally freely rotatable upon the shaft |30 but may be clutched thereto by means of a pneumatic clutch, indicated diagrammatically at |3|.

The transmission 51 `may be of vany suitable construction adapted to provide a plurality of manually selectable `torque multi- -plication ratios between the .torque converter .and the .hoisting drum. However, the transmission is preferably constructed .in .the manner more fully set forth in applicants copending application, Serial No. 602,619, filed concurrently herewith. .It is suicient to state here that this preferred form of transmisison is a compound planetary transmission which will provide eight different torque 4multiplication .ratios under the control of the operator and which may be shifted under full load without disconnecting the drive connections to the drum. The preferred transmission also incorporates van automatic two-speed transmission `for shifting kthe torque multiplication ration of the transmission .to a lower value when the output speed of the torque converter reaches a predetermined value.

VSince .the torque converter employed in connection Vwith all forms of the present invention must operate vcontinuously under stall conditions, or 'with theoutputshaft rotating reversely with respect to the input shaft during drilling operations, sufcient cooling mechanism must be provided to absorb all the energy delivered .to the torque converter in order to prevent .development of .excessive .or destructive temperatures. The preferred mechanism for this pur- .spaans .pose is a differentially operated cooling mechal nism of the type more fully set forth in applicants copending application, Serial No. 571,656, led January 6, 1945.

The operation of the apparatus illustrated diagrammatically in Fig. 4 is as follows: When it is desired to lower the drill stem into the hole, the connection between the engine and the differential is broken by disengaging clutch 62, and the connection between the differential and the transmission is likewise broken by disengaging clutch 1G. The speed at which the drill stem is lowered may then be controlled in any suitable manner but is preferably controlled by applying a braking force to the drum from the engine through the torque converter 50 and transmission :51, the amount of braking effort being adjustable by adjustment of the engine throttle and by adjustment of the torque multiplication ratio provided in the transmission 51. If desired, one or more of the additional engines which are connected to the drive chain |29 may be utilized to assist in the braking operating by engaging clutch |3| After the drill stem has been fed into the hole into position for drilling, if it is ,desired to operate with automatic control of the drill bit pressure, clutch |3| is disengaged and the remaining engines connected to the slush pumps in the usual manner. The clutches, 56, G2, and 10 are engaged. The torque multiplication ratio of the transmission 51 and the engine throttle position (or governor control setting if the engine is a governed engine) are then set at the desired values, in accordance with the principles outlined in connection with the first two forms of the invention described above. The drilling operation will then be started and the drill bit pressure will be vautomatically maintained at an optimum value for a given table torque, and will vary only in response to variations in table torque. Consequently, the apparatus will tend to stabilize at a constant table torque of any desired value.

As the drilling progresses deeper it will be necessary to adjust the engine throttle or governor setting from time to time and also to adjust the torque multiplication ratios provided in the transmission 51. If the engine 41 is not of the governed type referred to in connection with the second form of the invention described above, or does not employ a separate table driving engine, it will be necessary after an extended drilling period to adjust the torque multiplication ratio provided between the differential and drum. This may best be done by changing the relative sizes of the sprockets in the sprocket and chain connection 69 but, if desired, a change-speed transmission may be provided for that purpose.

When, during the drilling operation, it is necessary to reverse the rotation of the table, the brake band l2 is set to hold the planet cage in the reverse transmission 65 against rotation, and the clutch mechanism H8 is disengaged. The input shaft 59 of the transmission 65 may then be rotated either directly from the engine through the differential mechanism 54 or, if desired, through the torque converter 5|?. 'If a direct drive to the table is desired, the brake band |21 on the planet cage |26 of the overdrive and clutch mechanism 49 is released. This disconnects the engine from the torque converter. The engine 41 then drives through chain 6|, and the ,differential 64 to the shaft 59, and thence to the table. During such directdrive operations,

i? the third member, namely, the output shaft 68 of the differential 64 may be held stationary in any desired manner, as by application of the brakes 46 to the drum 45. If it is desired to drive the table through the torque converter, clutch 62 is disengaged, the brake |21 is set to hold the planet cage |26 of the overdrive and clutch member 49 stationary, clutch 6l) is engaged, and clutch 56 is disengaged. The torque converter then drives directly to the shaft 59 and thence to the table and the input shaft 63 of the diiferential mechanism rotates freely. It will be apparent that the same two methods of driving the table may be employed when the transmission 65 is not set to cause reverse rotation. In other words, the table may be driven either forwardly or reversely from the engine through either the torque converter or the differential without employing the automatic drilling features of the present invention. Thus the driller can control the weight of the drill stem manually through brakes 46, if desired.

It will be noted that the reverse drive provided by the transmission 65 is a torque multiplying reverse drive connection. This is desirable in order to increase the torque which may be applied either from the converter or differential to the table, in order to break joints in the .drill stem. The torque multiplication thus provided is further increased when the table is driven through the diierential by reason of the fact that the differential mechanism itself provides a torque multiplication, and it is increased when the table Ais driven from the converter by the torque ratio provided by the converter itself less the eifect of the overdrive connection 49. If a further increase in torque multiplication is required, the torque multiplication provided in transmission 65 by the gears lll-94 may be obtained by disengaging the clutch elements 91 and 98. During automatic drilling the desired torque ratio between the engine and the table may be obtained entirely by the torque multiplication provided in the differential or by the sprocket and chain connection 66 or both, in which event the transmission 65 will be set to provide a direct drive connection.

When it is desired to pull the drill stem out of a hole, all of the engines are tied into the shaft |30 by engaging clutch I3l, and the differential drive connection is disengaged by disengaging clutches 62 or 10, or both. Thus all of the engines, through individual torque converters, drive the hoisting drum through transmission 51.

It will be understood that the apparatus of Fig. 4 may include a separate engine for the table, as shown in Fig. 3, or a torque converter in the table drive as shown in Fig. 4, or both if desired. If a separate engine is not used the single engine may be either governor controlled or controlled by the usual fuel consumption control device in accordance with the principles heretofore outlined.

While the several forms of apparatus specii'lcally described employ internal combustion engines and hydrokinetic torque converters to control the drill bit pressure, the invention contemplates the ,use of any type of slipping torque transmitting coupling which will transmit a torque which is a function of the input speed and also contemplates the use of any source of motive It will be apparent that the several forms of invention illustrated and described provide relatively simple and practical means for automatiatea-11e cally controlling the pressure of the drill bit on the formation in such a manner as to maintain the table torque and drill bit pressure at a substantially constant value. If for any reason the table torque-increases the drill bit pressure will be relieved in approximate proportion to the increase in table torque and vice versa. Should the drill stem or bit encounter an abnormal resistance to rotation such as that caused by a falling boulder, or otherwise, the stem will be automatically elevated before the table torque reaches a value which will twist off the stem. Consequently, the apparatus prevents twist-ois and permits more rapid rates of rotation for the drill stem without danger. An important feature of the invention resides in the fact that it may employ apparatus, all the elements of which are reliable and standard mechanisms whose 'performance characteristics are well known. Moreover, the apparatus required to effect automatic drilling is to a very large extent the same apparatus required to perform the drill stem hoisting operations. Consequently, the cost of the apparatus is not high.

While several forms of the invention have been illustrated and described, it will be apparent that other variations in the design and construction may be indulged in without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. In an oil well drilling apparatus, a hoisting drum for supporting the drill stem, a rotary table transmitting connection between the other of said l differential output members and the table, and a torque transmitting connection between the output of the torque converter and the drum.

2. In an oil well drilling apparatus, a hoisting drum for supporting the drill stem, a rotary table for rotating the drill stem, an enine, a. hydrokinetic torque converter, a driving connection between the input shaft of the converter and the engine, a differential mechanism having an input member, a driving connection between the diierential input member and the engine independent of said converter, said differential having a pair of output members, a torque transmitting connection between one of the differential output members and the drum, a torque transmitting connection between the other of said differential output members and the table, and a torque transmitting connection between the output of the torque converter and the drum, selectively operable means for disconnecting the converter output from the drum, and a selectively operable reverse gear in the connection between said other differential output member and the table.

3. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a pair of independent rotary driving shafts, a torque transmitter operatively connected to and actuated by one of said shafts and connected to said drum for applying a torque 19 to said drum in a direction to support the drill stem, mechanism operatively connected to and actuated by the other driving shaft for rotating the drill stem simultaneously with the application of torque to said drum by said torque transmitter, and means operatively connected to said mechanism and to said drum for transmitting to the drum an additional torque in the same direction which is proportional to the torque transmitted by said mechanism to rotate the drill stem.

4. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stein, including a hoisting drum for supporting the drill stem, a rotary driving shaft, a torque transmitter having rotary input and output elements and being of the type which delivers a torque proportional to the speed of rotation of the input element when the output element is not rotating, a driving connection between said input element and said shaft, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, means for rotating the input member of the differential mechanism, a power takeoif for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum by said output element, and a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element.

5. Apparatus for operating a rotary well drilling machine and for correlating the drill fbit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a rotary driving shaft, a torque transmitter having rotary input and output elements and being of the type which delivers a torque proportional to the speed of rotation of the input element when the output element is not rotating, a driving connection between said input element and said shaft, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between said shaft and the input member of the differential mechanism, a power take-off for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum said output element, and a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element.

6. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a rotary driving shaft, a torque transmitter having rotary input and output elements and being of the type which delivers a torque proportional to the speed of rotation of the input element when the output element is not rotating, a driving connection between said input element and said shaft, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary assedic input member and a pair of rotary output members, a driving connection Ibetween said shaft and the input member of the differential mechanism, a power take-oli for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum by said output element, a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element, a prime mover for driving said rstmentioned shaft, and adjustable governing mechanism associated with said prime mover for maintaining the speed of operation of said prime mover substantially constant under varying loads at any selected one of a plurality of different speed levels.

7. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a rotary driving shaft, a torque transmitter having rotary input and output elements and being of the type which delivers a, torque proportional to the speed of rotation of the input element when the output element is not rotating, a driving connection between said input element and said shaft, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between said shaft and the input member of the differential mechanism, a power take-off for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum by said output element, a torque transmitting connection between the other differential output memberV and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element, and a change-speed transmission in the driving connection between said output element and the drum, said transmission being independent of the torque transmitting connection between said differential output member and the drum.

8. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a rotary driving shaft, a hydrokinetic torque converter having rotary input'and output elements, a driving connection between said input element and said shaft, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between said shaft and the input member of the differential mechanism, a power take-off for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum by said output element, a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element, and a change-speed transmission in the driving connection between said output element and the. drum, said trans- 2l"- 'mission 'beingindependent of `the torque transmitting connection between said differential output member andthe drum.-

9. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, apair of independent rotary driving shafts, a torque transmitter having rotary input and output` elements and being of the type which delivers a torque proportional to the speed of rotation of the input element when the output element is not rotating, a driving connection between said input element and one of said shafts, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between the other shaft and the input member of the diierential mechanism, a power take-off for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum yby said output element, and a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element.

l0. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a pair of independent rotary driving shafts, a hydrokinetic torque converter having rotary input and output elements, a driving connection between said input element and one of said shafts, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between the other shaft and the input member of the differential mechanism, a power take-off for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum by said output element, and a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element.

ll. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a pair of independent rotary driving shafts, a torque transmitter having rotary input and output elements and being of the type which delivers a torque proportional to the speed of rotation of the input element when the output element is not rotating, a driving connection between said input element and one of said shafts, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between the other shaft and the input member of the diierential mechanism, a power takeoff for rotating the drill stem -connected to and driven by one of theoutput members of the differential simultaneously with the application of torque to the drum by said output element, a

torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element, and separate prime movers connected to said shafts for driving the same, the prime mover connected to said one shaft having adjustable governing mechanism for maintaining the speed of operation of said prime mover substantially constant under varying loads at any selected one of a plurality of different speed levels.

12. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a rotary driving shaft, a torque transmitterv having rotary input and output elements and being of the type which delivers a torque proportional to the speed of rotation of the input element when the output element is not rotating, a driving connection between said input element and said shaft, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between said shaft and the input member of the differential mechanism, a power take-off for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum by said output element, a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element, a prime mover having an operating range in which its speed varies an an inverse function of its delivered torque, and a driving connection between said prime mover and said shaft, the torque multiplying ratios of said driving connections between the drum and both said output element and said other output member of the differential being so correlated with each other and the speed-torque characteristics of the prime mover that`0n any decrease in the speed of the prime mover induced by an increase in the torque required to rotate the drill stem the'l torque delivered from said other differential output member to the drum will increase by an amount greater than the decrease in the torque delivered to the drum from the output element.

13. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a rotary driving shaft, a hydrokinetic torque converter having rotary input and output elements, a driving connection between said input element and said ssaft, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between said shaft and the input member of the differential mechanism, a powertake-oif for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum by said output element, a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from Said ouput element, a prime mover having an operaing range in which its speedvariesas an inverse function of its delivered torque, land a driving connection between said prime mover and said shaft, the torque multiplying rotios of said driving connections between the drum and both said output element and said other outpt member of the differential being so correlated with each other and the speed-torque characteristics of the prime mover thaton any decrease in the speed of the prime mover induced by an increase in the torque required to rotate the drill stem the torque delivered from said other differential output member to the drum will increase by an amount greater than the decrease in the torque delivered to the drum from the outputl element.

14. Apparatus for operating a rotary well drilling machine and4 for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supporting the drill stem, a rotary driving shaft, a torque transmitter having rotary input and output elements and being of the type which delivers a torque proportional to the speed of rotation of the input element when the output element is not rotating, a driving connection between said input element and said shaft., a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, a driving connection between said shaft and the input member of the differential mechanism, a power take-oir for rotating the drill stem connected to and driven by one of the output members of the dierential simultaneously with the application of torque to the drum by said output element, a torque transmitting connection between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element, a disengageable clutch in the drive connection between said shaft and the drum through the torque transmitter, a brake for holding the drum stationary, and a selectively operable reversing transmission in they drive connection between said other output member of the differential and the drill stem rotating power take-01T.

15.. Apparatus for operating a rotary well drilling machine and for correlating the drill bit pressure with the torque required to rotate the drill stem, including a hoisting drum for supA porting the drill stem, a rotary driving shaft, a torque transmitter having rotary input and outiut elements and being of the type which delivers a torque proportional to the speed of rotation of the inputy element when the output element is not rotating, a driving connection between said input element and, said shaft, a torque transmitting connection between said output element and said drum, a differential mechanism having a rotary input member and a pair of rotary output members, means for rotating the input member of the differential mechanism, a power take-oli for rotating the drill stem connected to and driven by one of the output members of the differential simultaneously with the application of torque to the drum by said output element, a torque transmitting connecion between the other differential output member and the drum for applying an additional torque to the drum in the same direction as the torque transmitted to the drum from said output element, a disengageable clutch in the drive connection between said shaft and the input member ofY the differential, means including a selectively operable clutch for establishing a driving connection between said output element and the drill stem rotating `power takeoff, means including a disengageable clutch in the driving connection between the output element and the drum, and a selectively operable reversing transmission in the drive connection between the output element and the drill stem rotating power take-off.

CHARLES M. OLEARY.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,776,779 Bricken Sept. 30, 1930 1,795,706 Black Mar. 10, 1931 1,808,222 Hild June 2, 1931 1,836,998 Thullen Dec. 15, 1931 1,962,346 Hild June 12, 1934 2,051,249 Edwards Aug. 18, 1936 2,123,344 Rogers July 12, 1938 2,136,356 Hild Nov. 8, 1938 2,164,173 Durrell. et al June 27, 1939 2,282,597 Archer May 12, 1942 

